Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain,central Greece

1. Introduction

During the last few decades,many studies have been conducted regarding the Holocene stratigraphic configuration of several deltaic successions around the Mediterranean(e.g.,Amorosiet al.,2005; Boyeret al.,2005;Bruno et al.,2015;Pechlivanidou et al.,2014).The majority of the research is confined to seismic profile interpretations(e.g.,Lafuerza et al.,2005;Somoza et al.,1998;Styllas,2014),geochemical and sedimentological studies(e.g.,Pechlivanidou et al.,2014),and tectonics and geodynamics(e.g.,Lafuerza et al.,2005;Somoza et al.,1998;Styllas,2014).

The Sperchios delta plain is located in central Greece and covers an area of 121.5 km2.Several times in the past,the river's main channel shifted its course due to hydrological changes or tectonic activity in the Sperchios basin.These changes on the river's channel resulted in the development of many deltaic prolongations in the Maliakos Gulf and created an extensive deltaic plain due to the high rates of sedimentation(Poulos et al.,1997).

Previous studies in the Sperchios delta plain have mainly been conducted regarding the palaeogeography of the battle terrain in ancient Thermopylae,particularly concerning the reconstruction of the shoreline position at the time of the battle(Kraft et al.,1987;Tziavos,1977;Vouvalidiset al.,2010a).More recently,the palaeogeography of the Late Holocene Sperchios delta plain has been outlined by Pechlivanidou et al.(2014),with sedimentological,palaeontological,geochemical,and mineral magnetic property approaches to detect the palaeoenvironmental signal of Sperchios deltaic deposits.In this study it was estimated that the transition from lagoonal to terrestrial conditions and the development of the Sperchios delta plain tookplace around～6000 cal yr BP(Pechlivanidou et al.,2014)following the slowing rate of sea-level change as recorded across the broader region of the Aegean(Lambeck and Purcell,2005;Pavlopoulos,2010;Pavlopoulos et al.,2012).

During macroscopic observations,attention was usually paid to sediment color,grain size,textures,structures,etc.Regarding grain-size analyses,since that no continuous sampling was executed over the full cores length,it is impossible to discuss detailed grainsize grading trends.Sample selections for grain-size analyses as well as for luminescence dating were based on macroscopic observations(distinct sedimentary layers).In total,31 samples were collected for grain-size analyses.Grain-size analyses were conducted at the laboratory of sedimentology of the Hellenic Centre for Marine Research(“H.C.M.R.”),and using the Micromeritics®SediGraph 5100 device.The lithological characterization of each sample was obtained using triangular charts(Folk,1974).The results of grain-size analyses along with their lithological characterization are shown in Table 2 and Fig.3.Sediment color was distinguished visually by comparison with standard Munsell Soil Color Charts(Munsell color company,1994)and is reported in general terms.

Over the last three decades luminescence dating methods have been developed and now they are widely applied to dating sediments from different geological environments(e.g.,aeolian, fluvial and marine).In recent years,OSL(Optically Stimulated Luminescence)dating of fluvial deposits has gained much attention(e.g.,Theodorakopoulou et al.,2009;Zacharias et al.,2009)because of the advantage of directly determining the time elapsed since deposition,thus avoiding indirect dating using radiocarbon or other methods(e.g.,Wallinga and Bos,2010;Wallinga et al.,2010).Detailed reviews on the application of OSL dating on fluvial sediments are given in Wallinga(2002)and Rittenour(2008).

Although OSL dating is now widely applied to a wide range of sedimentary environments,its application on fluvial deposits is still limited,since such deposits may have the problem of incomplete bleaching of grains.Grains transported by fluvial processes may not be fully bleached,as water turbulence and short transportation do not allow for a complete resetting of the OSL signal(Ditlefsen,1992;Rendell et al.,1994).During burial diagenesis,the OSL signal builds up again adding to a residue signal and resulting in a broad distribution of the equivalent dose(DE).

A number of different methodologies that can assist in obtaining the best estimate of DEare nowadays available(e.g.,Lepper and McKeever,2002;Olley et al.,1998;Stokes et al.,2001),and of these the most widely used,are the “age models” of Galbraith et al.(1999).These models are based on statistical analysis ofthe DEvalues and their validity has been demonstrated in empirical and modeling studies(e.g.,Arnold et al.,2009;Bailey and Arnold,2006).Galbraith and Roberts(2012)provide a review of the statistical characteristics that are used to obtain the best DEvalue.

The Sperchios basin chiefly comprises the Paleocene—Eocene flysch formations,mainly appearing in the western and southern parts of the basin(～46%of the total area).Extended limestone formations can be found in the eastern and southern parts of the basin(～14%of the total area),while ophiolite and molasse formations cover the central mountainous part(～11%of the total area).The Sperchios River valley area,as the central part,is covered by the Quaternary unconsolidated fluvial deposits,including the Holocene deltaic sequences(Fig.1).

在这个大数据的时代，机遇和挑战是共存的，因此，变化是这个时代催生的产物，同时寻求发展是这个时代永恒不变的话题。当今社会是一个信息化、网络化的社会，大数据是这个时代最完美的发明，这项发明在测绘地理信息中发挥着巨大的作用，因此，只有合理地运用大数据带来的便利服务，才能把握好机遇，同时也会将挑战变为发展。

2. Study area and core description

The Sperchios delta plain embraces part of an active rift system formed by an extensional deformation of the Greek mainland since the Early Pliocene(～5 Ma)(Kilias et al.,2008).The rift was characterized by an asymmetric half-graben(Eliet and Gawthorpe,1995)mainly controlled by movements of its active fault boundary along its southern margin.The main fault system which has determined the topography of the area is located in the southern part of the Sperchios basin and can be subdivided into two different parts:(1)the Sperchios—Ipati fault zone located in the west,abutting the valley of the Sperchios River to the south,and(2)the Kamena Vourla—Arkitsa fault zone in the east,abutting the Maliakos basin to the south(Eliet and Gawthorpe,1995;Kilias et al.,2008).Fault tectonism took place at the end of the Pliocene and the beginning of the Pleistocene periods,and continues to the present.Due to neotectonic movements,the Pliocene deposits developed in the south of the Maliakos Gulf,had been uplifted by more than 500 m(Gartzos and Stamatis,1996;Maroukian and Lagios,1987),where a vertical displacement of about 1800 m has been suggested for the southern boundary of the Sperchios River catchment area,as a result of intense tectonic activity during the Quaternary(Maroukian and Lagios,1987).

In this study,we investigate the applicability of OSL dating on sand-sized quartz to construct a reliable chronological framework for the upper(～20 m)sediments of the Sperchios delta plain.Here we present a new chronology for the Sperchios delta plain and provide sedimentation rates of its depositional sequences during the Holocene.Taking into account that limited light exposure prior to deposition and burial of the quartz grains may result in incomplete resetting of the OSL signal,we employed statistical approaches for obtaining reliable DEestimates.

Previous studies have indicated that terrestrial sediments were found at the deepest parts(～40 m.b.s.l.)in the central part of the present Sperchios delta plain and represent fluvial sediments accumulated probably during the Late Quaternary or during the earliest stage of the last transgression around the Pleistocene—Holocene boundary,when the rate of sea-level rise was outpaced by the sediment accumulation rate(Pechlivanidou et al.,2014).

Sea-level rise during the Early Holocene(Lambeck and Purcell,2005;Pirazzoli,1996;Vouvalidis et al.,2005) flooded the area of the present delta plain and created sediment successions comprising coastal sediments and distal prodelta deposits(Pechlivanidou et al.,2014).During the Middle—Late Holocene,deceleration in sea-level rise favored the progradation of the Sperchios delta and a shift back to terrestrial conditions,as sediment supply exceeded the relative rate of sea-level rise.

Different sedimentary facies represent different palaeoenvironmental changes across the Sperchios delta plain.Terrestrial sediments represent the fluvial processes,while,the presence of molluscan shell fragments probably indicates the rising sea-level conditions and a coastal environment.Our research samples,extracted through coring described as below,comprise the sedimentary facies of the Holocene transgressive—regressive strata overlying the Late Pleistocene deposits that followed the general stratigraphic development of the Holocene Mediterranean deltas(Stanley and Warne,1994).Selections of coring locations were based on the proximity of each borehole to the Sperchios River and current coastline,to achieve a good representation of the diachronic sedimentary processes that have taken place in the Sperchios basin.And,the Holocene depositional sequences of the Sperchios delta plain were studied on the basis of samples from these five cores(Fig.1).

The basic information of the five cores is given in Table 1.

Coring instruments included a truck-mounted hydraulic rotary rig with an auger being pushed in using hydraulic power or percussion,if needed(Fig.2a)and a vibra coring unit with a vibrating motor used to assist in driving the core barrel into the sediment(Fig.2b).The auger used a 7.5 cm lined bore.Throughout the drilling operation,the boreholes were sleeved in order to prevent the collapse of sediment into the borehole and avoid sampling disturbed sediments.The retrieved core samples were immediately capped.

Based on such considerations,we applied the Minimum Age Model(MAM)suggested by Galbraith et al.(1999)to determine the appropriate DEvalue.The MAM can be used for heterogeneous bleached samples and can identify the well-bleached aliquots by applying a truncated normal distribution to the log DE values(Galbraith and Laslett,1993;Galbraith et al.,1999).The width of this minimum DEdistribution is derived from statistical measurement errors of each DE value and the over-dispersion.

在大数据环境不断优化的背景下，档案局应更加注重科学技术在档案管理及保护工作中的应用，要选用有专业素养的人才。只有在专业素养人才的带领下才能建立起专门的档案保护部门，使整个部门的工作人员认清档案管理及保护的工作规划、工作形势和工作步骤。首先，要提高现有档案管理工作人员的专业素养，对工作人员进行培训，在培训过程中要注意到每个工作人员存在的问题，并单独解决每个员工的不足。其次，要招聘新的有专业素养的人才，应能够对以前档案管理存在的问题提出解决意见。

Deceleration in sea-level rise favored the progradation of the delta,as the rate of sediment supply outpaced the rate of sea-level rise.The shift back to terrestrial conditions is estimated to have started soon after 4.7±0.5 ka(sample GT1-9)for the south—central part of the basin.These conditions are represented by deltaic deposits dominated by fine-grained(clay)sediments and the complete absence of molluscan shells.

However,little effort has been made so far to reconstruct the comprehensive and sequential history of the upper part of the Sperchios delta plain based on numerical age data,with the available ages mainly based on archaeological and radiocarbon dates which bear a range of limitations and uncertainties(e.g.,sample contamination and inaccurate estimation of the ratio of14C—12C).Previous chronological studies for the delta(Pechlivanidou et al.,2014;Vouvalidis et al.,2010b)remain limited in literature.Thus,a systematic application of dating techniques is required,which would provide an insight into the Holocene geomorphologic history of the area by establishing the chronology of the region.

In total,19 samples were collected from the five cores at varying depths,among which the deepest one was up to 14 m.b.s.l.(Fig.3,GT1-19.8),for optically stimulated luminescence dating.

3. Luminescence dating

3.1. Sample preparation and measurement facilities

Samples collected from the five cores were submitted to the Luminescence Dating Laboratory of the National Centre for Scientific Research,“Democritos”Greece,where they were opened under subdued red light conditions to obtain samples for OSL analysis.For each core sample,one half was brought into light for macroscopic observations and grain-size analyses,and at the same time,to select suitable depth intervals for OSL sampling.However,the OSL samples were taken from the other half of the core.

We tried to sample sandy intervals and avoid sampling closely to the interval boundaries to facilitate reliable estimation of the gamma dose rate.Each sample taken for luminescence dating represents～8 cm of core length.The outer 1 cm of the sediments was discarded to avoid possible contamination of disturbed sediments while recovering the core.

对于淳安而言，探索“保水渔业”带来的深层次意义，是“像保护眼睛一样保护千岛湖”成为全县共识，由其引发的一场护水“保卫战”，在千岛湖全域系统展开。

Quartz is commonly the preferable mineral in OSL dating of fluvial deposits,as its residual signals are usually lower than those for feldspar(e.g.,Fiebig and Preusser,2007),and the quartz OSL signal is more stable over geological timescales(Wintle and Murray,2006).We chose sand-sized grains for DEdetermination as these allow OSL measurements on aliquots containing only a few grains,which facilitates better interpretation of the completeness of OSL resetting prior to deposition and burial(e.g.,Duller,2008).

Following conventional laboratory practices(e.g.,Preusser et al.,2008),quartz coarse-grains were prepared using the procedure of chemical treatment with 10%hydrochloric acid to remove carbonate cements and 10%hydrogen peroxide to remove organic content,and then were dried and sieved.Fractions were treated with 40%hydro fluoric acid to avoid contribution of the alpha-irradiated outer part of the mineral,followed by a rinse with 10%hydrochloric acid to remove fluorosilicate and a final sieving to separate traces of any remnant byproducts.Purified quartz grains which were treated with 40%hydro fluoric acid for 90 min to remove all other minerals mainly fell in the range of 80—125μm.

The reliability of these measuring parameters was further confirmed by a dose recovery test undertaken on aliquots from two samples.Six aliquots of sample GT1-3 and six aliquots of GT2-17.5 were bleached by sun exposure for 6 h and then an 11.5 Gy dose was given.SAR protocol was then applied to the test if the 11.5 Gy dosecouldbe recovered.For a well performing SAR protocol,the ratio between the measured dose and the given dose should be close to unity(Murray and Wintle,2003),at least be in the range of 0.9—1.1.The test showed that recovery ratios were within the 2σlevel(0.9—1.1;Fig.7).The mean ratio(N=6)of the given dose to the recovered DEwas 0.97±0.03 for sample GT1-3 and 0.98±0.01 for sample GT2-17.5(Fig.7;the dashed line),signifying that the SAR protocol generates a well equivalent dose accuracy and precision.Furthermore,all“recycling ratio” values for the same aliquot were within±5%of unity(mean ratio 0.97±0.04).That is,we consequently performed the SAR protocol as described in Table 3.

Measurements were carried out on a Risø TL-DA 15 luminescence reader fitted with a Thorn EMI photomultiplier tube.Irradiation was from a calibrated 90Sr/90Y β source.Blue LEDs(470 nm)were used for stimulating the aliquots and a 7.5 mm Hoya U-340 filter was the signal detection filter mounted in front of the photomultiplier tube.The single-aliquot regenerative dose(SAR)protocol after Murray and Wintle(2003)was applied for DEmeasurements(Table 3).

对于非常规油气资源，埃克森美孚的核心是美国本土二叠纪盆地，主要通过并购手段来扩大页岩资产。2016年埃克森美孚并购巴斯家族二叠纪盆地资产后，埃克森美孚在二叠纪盆地核心区域新增面积27.5万英亩，新增优质页岩油资源量60亿桶，从而使得埃克森美孚在二叠纪盆地的页岩油资源量达到95亿桶，大大巩固了埃克森美孚的非常规资产厚度。

3.2. Dose rate determination

To avoid potential problems related to an inhomogeneous gamma radiation field,OSL samples were taken from thick lithological-homogeneous sediment layers and far from lithological boundaries.Besides,a separate sample for dose rate analysis was taken over the entire range of the luminescence sample.

The calculation of the dose rates(U,Th,K)was based on analytical data obtained by Inductively Coupled Plasma Mass Spectrometry(ICP-MS;ACME laboratories,Canada)and using the“The Dose Rate calculator”(DRc)software developed by Tsakalos et al.(2016).The DRc uses the conversion factors proposed by Guérin et al.(2011)and the attenuation factors(due to water content)for alpha radiation by Aitken(1985),beta radiation by Nathan and Mauz(2008),and gamma radiation by Guérin and Mercier(2012).DRc also calculates the cosmic ray contribution to the total dose rate according to Prescott and Stephan(1982)and Prescott and Hutton(1988,1994)using the altitude and latitude of the sampling site,its present-day depth and the density of the overburden.The final dose rates are obtained by correcting for the acid etching of grains and the grain size.Sediment water content was determined using the present water content with an error of±5%and considered to remain constant during burial.The dose rates are listed in Table 4.

3.3. OSL measurements

A typical decay and a dose—response curve for one aliquot(sample GT1-19.8)from the coarse-grain(80—125 μm)quartz is shown in Fig.4.A measure of the residual IRSL(infrared stimulated luminescence)to detect feldspar contamination was also incorporated at the end of each sequence.No signal response was observed during infrared stimulation,which was carried out for each aliquot at the end of a measurement sequence.Therefore,it is concluded that a significant feldspar contamination is unlikely in the quartz samples investigated in this study.

3.3.1.Validation tests

实体面积计算实质就是平面拟合算法，实体面积也就是该水平面的面积。点击CASS9.0软件菜单栏里的“工程应用”下的“计算制定范围的面积”命令，根据提示选用窗选方式进行 圈定需计算面积的地物；选择图层，该图层实质是封闭复合线在某个平面的投影；最后再选择指定图层的目标，此时窗选会系统自动过滤，只计算注记指定图层被选中的以复合线封闭的地物，将自动弹出所选区域内地物的实体面积，见图2。

Prior to standard dating using the SAR procedure,the performance of the protocol parameters was confirmed by a preheat plateau test(Murray and Wintle,2000)and a dose recovery test(Murray and Wintle,2003)(Figs.5—7).

As shown in the steps of the SAR protocol(Table 3),a high temperature is applied before the Blue-LED stimulation.This is necessary so that electrons accumulated in any thermally unstable traps will be thermally stimulated and released,preventing their unwanted contribution to the stable OSL signal that will be measured in the next step of the SAR protocol.If an unwanted signal contributes to the OSL signal,it will result in an increased DEand therefore get a wrong overestimated age.A preheat plateau test shows that if there is any unwanted contribution to the stable OSL signal,it will cause erroneous DEdetermination(Wintle and Murray,2006).In the preheat test,a number of DEvalues are determined using different preheat temperatures(Murray and Wintle,2000;Roberts et al.,1999);and the preheat temperature which is taken for measurement should be obtained in a plateau.Since the examined samples may be bleached,the scattered DEdistribution would be expected,thus obtaining the right preheat plateau is difficult.In this study we used a combination of preheat and dose recovery test which can overcome this problem.For this test,aliquots of two samples were bleached in the OSL reader using Blue-LEDs for 40 s to reset the natural signal(e.g.,Athanassas,2011;Kunz et al.,2013;Trauerstein et al.,2017).The bleached aliquots were then irradiated with a fixed β-dose of 11.5 Gy and measured at various preheat temperatures(20 °C spacing)ranging from 200 °C to 300 °C with a cut-heat at 200°C.The measured(or recovered)dose is almost equal to the given dose,i.e.,the ratio of the measured dose versus the given dose is close to unity(value of 1),between temperatures 220°C and 240°C(Fig.5),and the former temperature was selected for the subsequent measurements.The recycling ratios were systematically consistent with unity(ranging from 0.98 to 1.05)and the recuperation never exceeded 2%.

Many chronological studies(e.g.,Madsen et al.,2005;Wintle and Murray,2006)have shown that quartz samples can be affected by thermal transfer.An approach similar to the preheat-dose recovery test was applied,during which no artificial irradiation was given,at various cut-heat temperatures between 140 °C and 240 °C(with a preheat at 240 °C)to examine if thermal transfer is apparent.Results clearly show that the equivalent dose(DE)is insensitive to cut-heat temperatures between 140°C and 200 °C,resulting in the selection of the 200 °C temperature for cut-heat for all quartz samples.And,for cut-heat temperatures from 220 °C to 240 °C,the DE increased around 0.5 Gy(Fig.6).

Single aliquot measurements carried out on small aliquotsare assumed better to reflectany inhomogeneities in the equivalent dose distribution than using larger aliquots(e.g.,Fuchs and Wagner,2003;Olley et al.,1998).Thus,for each sample,at least 12 aliquots were measured using aliquots with only the central 2 mm diameter covered with quartz grains.

选取聚类中心的个数K1=5,以PASCAL VOC中车、人、自行车三类数据集的目标框作为初始数据输入,实验得到的预测框比例如表3所示。

4. Results and discussion

4.1. Determination of the DEvalue based on statistical models

The establishment of the SAR protocol has revealed that different aliquots of the same sample give different equivalent doses.And this brought up the matter of how the equivalent dose(DE)distribution of a sample is to be depicted in order to get a meaningful and reliable representation and thus extract the necessary information for age calculations.A simple way of getting a first impression of how the equivalent doses are distributed is to produce a probability density function(PDF).However,the influence that an individual DEvalue distributed upon the overall distribution cannot be seen and examined in a single PDF.To avoid the uncertainty inherent in PDFs,Galbraith et al.(1999)developed the “radial plot” for the presentation of single-aliquot data.

在高速公路桥梁施工中，技术部门要对伸缩缝施工工艺予以详细认知，且要整合质量管理机制，确保质量控制体系能发挥其实际价值，实现管理水平的全过程优化。

The variety in DEdistributions can indicate that a sample was subjected to diverse bleaching conditions(Arnold et al.,2007;Olley et al.,1999;Rodnight et al.,2006) and post-depositional processes, and/or millimeter-scale differences in the beta dose rate to individual grains(Jacobs and Roberts,2007)or even intrinsic differences in the luminescence sensitivity of the measured aliquots.

Dating of deltaic sediments utilizing luminescence techniques could be problematic.Because of the transport—deposition mode of such sediments,sunlight exposure for the mineral grains might be not long enough to release any stored energy completely from the crystal lattice prior to deposition.In heterogeneously bleached samples,such as fluvial sediments,the DEdistribution generally shows larger variability(e.g.,Arnold et al.,2007;Olley et al.,1999;Rodnight et al.,2006).This has brought up the matter of how the best estimate of DEcould be extracted and used for age calculations.

Different approaches and methodologies have been proposed for assisting in obtaining the best estimate of the DE(e.g.,Galbraith et al.,1999;Lepper and McKeever,2002;Olley et al.,1998;Stokes et al.,2001),and of these the most broadly used are the“Age Models” developed by Galbraith et al.(1999).Many studies used over-dispersion values as the only diagnostic criterion for the choice of the most appropriate methodology(e.g.,Olley et al.,2004a).This value gives an estimate of the relative standard deviation of the true DE,remaining after the measurement error of each aliquot has been taken into account;if the measurement error was the only reason for the variation observed in DE,then the over-dispersion would be zero.Theoretically,for a well-bleached and homogeneous sample,an over-dispersion value close to zero would be expected.However,in a study testing the accuracy of various statistical models,Bailey and Arnold(2006)concluded that the selection of the most appropriate methodology based only on a single descriptor for the DEdistribution(such as the degree of over-dispersion)is not possible,and that no single analysis method is applicable to all samples from different depositional environments;and they proposed that the decision process should include a series of criteria which could describe the shape of the DE distribution(skewness,kurtosis,over-dispersion)and the presence of negative DEvalues.Bailey and Arnold(2006)also developed adecision processguide(Bailey and Arnold,2006;page 2500)that can be used to help choose the most suitable methodology on a case-by-case basis.

(3) 在排水管壁试样面积大小、水力梯度一致的情况下，与残积砾质黏性土相比，残积砂质黏性土的单位体积含土量增长了20%～36%，残积粉质黏性土的单位体积含土量增长了43%～73%，排水管壁试样单位体积含土量随着土体中黏粒含量的增大而增大，且增大幅度较其他两种变量大。

In our study,the DEdistributions of the measured aliquots clearly show a significant scatter with values of skewness ranging from 0.2 to 2.8,kurtosis ranging from 0.2 to 1.9,and over-dispersion values ranging from 15%to 29%(Table 5),which may be considered as typical for fluvial sediments(e.g.,Arnold et al.,2009;Olley et al.,2004b;Rodnight et al.,2006).

院校应该深刻认识到校企合作模式是建立在企业与学校互惠互利基础之上的一种合作共赢机制，其目的是跟随时代发展的潮流培养理论和技能全面发展的高素质人才，在确保学生就业率的同时提升学校的影响力。院校管理层应该积极进行校企合作模式的宣传和普及力度，让学生和老师都充分认识到校企合作的意义和优势，在具体的教学过程中同企业形成紧密的联系，形成科学的校企合作模式，积极进行沟通交流让学生收获更多的知识和经验。

Aliquots of two samples are depicted in radial plots along with their MAM calculated DEvalue in Fig.8.Here,DEvalue of each aliquot is displayed along with its associated relative standard error and precision.

The descriptive statistics which facilitated the age model decision procedures based on Bailey and Arnold(2006)and the range of OSL derived DEvalues are shown in Table 5.Table 5 also compares the DEvalues derived using the MAM with the mean and the weighted mean values.Data indicate that differences between the mean DEvalue and the MAM DEvalue range from 20%to almost 80%,while the weighted mean dose estimates differ from about 5%to 60%comparing to MAM DEvalues.In all samples,MAM produced smaller DE values than the mean and weighted mean values,and produced a reduction in the associated DEerrors.

在行政事业单位内部控制中加强财务监督工作，是我国事业单位发展的必然趋势。相关部门应该引起重视，可以采取加强预算控制力度、健全财务监督的相关机制、完善会计基础工作、提高财务监督人员的整体素质等措施来提高财务监督在行政事业单位内部的运用水平，进而为行政事业单位的健康发展奠定良好的基础。

4.2. Age estimates and sedimentation rates

Equivalent doses,dose rates and resulting OSL ages for all samples are given in Table 6;ages are given with 1-sigma(1σ)confidence interval,including all random and systematic uncertainties.Agesrange from 14.1±0.9 ka to 0.6±0.1 ka and indicate an Early—Late Holocene deposition.Dating results for the five cores are in correct chronostratigraphic order(within uncertainties)as the deepest sample in each core shows the oldest age estimate.The reliability of the OSL ages can additionally be supported by independent previous chronological studies conducted in the area.14C dating on marine shells collected through coring in the region of the delta(Pechlivanidou et al.,2014)gave similar ages at the corresponding depths.Particularly,core samples GT1-9 and GT3-5.8 gave ages of 4.7±0.5 ka and 3.8±0.6 ka respectively at depths of 3 m.b.s.l.and 3.8 m.b.s.l.They were collected at proximal(comparable)spots and similar depths to the sp1 and sp4 core samples of Pechlivanidou et al.(2014)at depths of 2 m.b.s.l.and 2.3 m.b.s.l.which were dated as 1403±113 cal yr BP and 1778±108 cal yr BP respectively,indicating a common Late Holocene deposition.

The sedimentary facies of the Sperchios delta represent transgressive to regressive sequences,overlying on Late Pleistocene—Late Holocene deposits.Terrestrial sediments probably represent fluvial sediments accumulated during the Early(8.7±1.1 ka as sample GT1-19.8 shows)to Middle(6.8±0.7 ka as sample GT1-14.5 shows)stages of the Holocene regression in the south—central part of the present delta,when the rate of sea-level rise was surpassed by the sedimentation rate.In the north—central part of the basin(core GT3),terrestrial sediments(most probably fluvial)were dated as 6.9±1.0 ka(sample GT3-13.7)to 3.8±0.6 ka(sample GT3-5.8)representing the Middle—Late Holocene deposition.These terrestrial deposits are found from～14 m.b.s.l.to～8.5 m.b.s.l. in the south—central part and～11.7 m.b.s.l.to ～3.8 m.b.s.l.in the north—central part of the Sperchios basin.Pechlivanidou et al.(2014)also dated fluvial sediments derived from a 40-m.b.s.l.borehole and suggested that these deposits represented the beginning of the last transgression around the Pleistocene/Holocene boundary.Further,Tziavos(1977)found that fluvial sediments developed under the present delta plain near Anthili(central part of the delta)at～37 m.b.s.l.,which indicate the occurrence of the Sperchios alluvial plain prior to the Holocene transgression.

Under the sea-level rising conditions and when the rate of sea-level rise outpaced sediment supply rate,the gradual flooding of the study area started.This is indicated by the presence of molluscan shell fragments,most probably suggesting a coastal/lagoon environment.The OSL ages assign these conditions from 5.8±0.7 ka(sample GT1-12)to 4.7±0.5(sample GT1-9)for the south—central part of Sperchios basin and soon after 3.8±0.6 ka(sample GT3-5.8)for the north—central part of the basin.Regarding the south part of Sperchios basin(core GT2),the total absence of molluscan shell fragments indicated that the sea did not reach this part of the basin during the last 14.1±0.9 ka.

Three cores were derived from the central part of the Sperchios delta plain using the truck-mounted hydraulic rotary rig and two cores were from the lower part of the Sperchios delta plain by vibra coring;the maximum drilling length was 20 m.All core depths are recorded as meters below sea-level(m.b.s.l.).A simplified diagrammatic representation of these five cores is provided in Fig.3,based on macroscopic observations and grain-size analyses.

（ 来源：《人民日报》 2018-08-03 http://country.people.com.cn/n1/2018/0803/c419842-30205811.html )

For the eastern part of the basin(next to current coastline),a shift back to coastal conditions indicated by the presence of molluscan shell fragments,started at～0.6±0.1 ka(sample KR7-1).

The data can be used to determine sedimentation rates occurred in the Sperchios delta plain;however,several limitations in such calculations exist,including factors such as surface run off and tectonic subsidence,among others,that act as substantial moderators of the sedimentation rate of an area.Nevertheless,in the present study,they cannot be examined and incorporated in the calculations of sedimentation rates;consequently sedimentation rates provided here should be considered with caution.OSL ages are plotted against the corresponding core depth in Fig.9.Six ages from two cores(GM5 and KR7)collected at the downstream part of the delta,in close proximity to the current coastline,define a nearly linear sedimentation rate ranging from～0.7 mm/yr over the deepest 3 m to～2 mm/yr over the upper 1 m.The mean sedimentation rate for the upstream part(cores GT1,GT2 and GT3)of the basin during the Middle—Late Holocene(～7—2.2 ka)was calculated at～2.6 mm/yr.For the south—central part of the basin(core GT1),sedimentation remains constant until～8.7 ka(full length of the core GT1).

Despite the fact that sedimentation in the Sperchios basin is mainly controlled by sea-level variations,one might expect that the significant local tectonisms may have resulted in a different depositional regime and stratigraphic architecture at its southern margin.A distinct break and a large reduction by a factor of～0.7 mm/yr sedimentation rate at ～15 m for the southern margin(core GT2)of the Sperchios basin are evident at～7 ka(Fig.9).Different sedimentation rates identified in core GT2 may be interpreted as the result of sediment supply from laterally sourced depositional systems which were controlled by several active normal fault segments of the Sperchios basin.

Furthermore,the striking change observed in sedimentation rates at～7 ka may indicate the transition to terrestrial conditions and the development of the Sperchios delta plain following the deceleration in the rate of the sea-level rise recorded across the broader region of the Aegean(e.g.,Stanley and Warne,1994).This is in agreement with previous studies in this area(e.g.,Pechlivanidou et al.,2014)and also with studies conducted in other deltas in the Mediterranean(e.g.,in the Rhone delta,Boyer et al.,2005;and,in the Aliakmon delta,Styllas,2014).

5. Conclusions

1)Since the increase of experience on effective absolute dating studies of fluvial—deltaic formations by employing the OSL technique is still on demand,the present study was mainly focused on the methodological approach that would allow accurate and precise absolute dating ages to be produced.From the depositional environment,incomplete bleaching of the samples was expected;and the methodological approach was proven from the DEdistributions and statistical parameters.

From a methodological perspective,this study suggests that:(1)the luminescence SAR approach utilizing quartz grains on small(2 mm)aliquots is a viable method to determine the burial age of deltaic deposits.And,(2)DEdistribution analysis based on statistical parameters allowed the choice of the appropriate statistical model which led to precise DE values and to reduction of the associated age errors.

2)Furthermore,this study suggests that luminescence dating offers excellent potential for establishing a chronological framework for the depositional sequences of the Sperchios delta plain.For the first time,absolute dating information based on luminescence dating of deltaic deposits was obtained in the region.

近年来，通过立足本地，走可持续发展路线，本专业与湖北心连心药房、武汉九州通、杭州天天好等企业进行紧密合作，建立实习与就业一体化的合作机制，利用企业和学校两种截然不同的教育资源，丰富教学内容，优化实践项目，如社会药房建立药历，即用药档案，对患者进行追踪服务，这是以前药学服务中所没有的项目，如今在很多社会药房都已经顺利实施，这种改变是服务领域扩展的具体表现形式之一。校企合作，转变了学生的就业观念，扩展了药学服务的领域，增强了毕业生的就业竞争力，也对培养符合社会需求的高职人才奠定坚实的基础。

3)The chronology for the five cores in this study shows that deltaic sediments were deposited during the Holocene.A relatively rapid deposition is implied for the top～14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions,while on the deeper parts the reduced sedimentation rate may indicate a lagoonal or coastal environment.

Acknowledgements

许沁走了，葛局长安静了下来，开始担忧了。想到许沁胜券在握的语气，不禁更担忧了。税务局长哪有屁股干净的？不只许沁懂，地球人都懂。但是，帮许沁是绝对不可能的。葛局长对许沁恨之入骨，绝不肯做违背个人意志的事情。可是，如果不帮许沁，她必定要在那段录音上做文章，问题就闹大了。许沁有句话说得没错，即使钻戒还了，他也是有前科的人。有前科的人，就会进入办案人员的视线。打铁还需自身硬，葛局长知道自身并不硬。许沁现在就像是定时炸弹，让他感受到了巨大威胁。

This study has been supported by the Greek General Secretariat of Research and Technology through ESPA-KRIPIS Project:“Development of an integrated management framework of river basins and associated coastal and marine zone”.

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